The provided code snippet appears to be an incorrect representation of a `UINavigationController` class. The properties and methods included do not match those found in the actual Swift documentation or Apple's official API.

Implementing Push and Pop Navigation Behavior Reusing Same View Instances for Enhanced Performance and Reduced Memory Usage.

Understanding iOS 6 Storyboard Rotation Issues and Workarounds for Landscape-to-Portrait Transitions

Customizing the Appearance of iOS Navigation Controllers' Back Buttons